package frame.core;

import frame.pojo.BoundSql;
import frame.pojo.Configuration;
import frame.pojo.MapperStatement;
import frame.utils.GenericTokenParser;
import frame.utils.ParameterMapping;
import frame.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

/**
 * FileName: SimpleExecutor
 * Author:   xuan zongjun
 * Date:     2020/11/6 12:05
 * Description:
 */


public class SimpleExecutor implements Executor {
    private Connection connection = null;



    @Override
    public <E> List<E> query(Configuration configuration, MapperStatement mappedStatement, Object[] param) throws Exception {
        //1、注册驱动，获取连接
        connection = configuration.getDataSource().getConnection();
        //2、获取sql语句：select * from user where id = #{id} and username = #{username}
            //转换sql语句： select * from user where id = ? and username = ? ，转换的过程中，还需要对#{}里面的值进行解析存储
        String sql = mappedStatement.getSql();
        //转换字符把 #{} 和 ${} 转换为 ？ ，并且获取 #{} 和 ${}中间的字符串
        BoundSql boundsql = getBoundSql(sql);

        // 3.获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement( boundsql.getSqlText() );
        Class<?> parameterTypeClass = mappedStatement.getParameterType();

        // 4. 设置参数
        List<ParameterMapping> parameterMappingList = boundsql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get( i );
            String content = parameterMapping.getContent();//#{} 中的参数
            //反射
            Field declaredField = parameterTypeClass.getDeclaredField( content );
            //暴力访问
            declaredField.setAccessible( true );
            //获取指定字段在实体类的值
            Object o = declaredField.get( param[0] );
            preparedStatement.setObject( i+1,o );

        }

        //5、执行sql，返回查询结果
        ResultSet resultSet = preparedStatement.executeQuery();
        //获取返回值的类
        Class<?> resultTypeClass = mappedStatement.getResultType();

        ArrayList<Object> objects = new ArrayList<>();

        // 6. 封装返回结果集
        while(resultSet.next()){
            //根据类的class创建具体类
            Object o = resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                // 字段名
                String columnName = metaData.getColumnName( i );
                // 字段的值
                Object value = resultSet.getObject( columnName );
                //使用反射或者内省，根据数据库表和实体的对应关系，完成封装，PropertyDescriptor 是内省库中的类
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor( columnName, resultTypeClass );
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke( o,value );

            }
            objects.add( o );

        }

        return (List<E>) objects;
    }


    /**
     * 完成对#{} 的解析工作，1 将#{} 使用? 代替， 2。解析出#{} 里面的值进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql){
        //标记处理类：配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser( "#{", "}", parameterMappingTokenHandler );
        //解析出来的sql
        String parse = genericTokenParser.parse( sql );

        //#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        return  new BoundSql(parse,parameterMappings);
    }


    @Override
    public void close() throws SQLException {

    }



}
